One of the principal mechanisms by which cellular regulation is effected is through the transduction of extracellular signals into intracellular signals that in turn modulate biochemical pathways. Examples of such extracellular signaling molecules include growth factors, cytokines, and chemokines. The cell surface receptors of these molecules and their associated signal transduction pathways are therefore one of the principal means by which cellular behavior is regulated. Because cellular phenotypes are largely influenced by the activity of these pathways, it is currently believed that a number of disease states and/or disorders are a result of either aberrant activation or functional mutations in the molecular components of signal transduction pathways.
For example, the polypeptide cytokine tumor necrosis factor (TNF) is normally produced during infection, injury, or invasion where it serves as a pivotal mediator of the inflammatory response. In recent years, a number of in vivo animal and human studies have demonstrated that overexpression of TNF by the host in response to disease and infection is itself responsible for the pathological consequences associated with the underlying disease. For example, septic shock as a result of massive bacterial infection has been attributed to infection-induced expression of TNF. Thus, systemic exposure to TNF at levels comparable to those following massive bacterial infection has been shown to result in a spectrum of symptoms (shock, tissue injury, capillary leakage, hypoxia, pulmonary edema, multiple organ failure and high mortality rate) that is virtually indistinguishable from septic shock syndrome (Tracey and Cerami, Annu. Rev. Med., 1994, 45, 491-503). Further evidence has been provided in animal models of septic shock, in which it has been demonstrated that systemic exposure to anti-TNF neutralizing antibodies blocks bacterial-induced sepsis (Tracey and Cerami, Annu. Rev. Med., 1994, 45, 491-503). In addition to these acute effects, chronic exposure to low doses of TNF results in a syndrome of cachexia marked by anorexia, weight loss, dehydration and depletion of whole-body protein and lipid. Chronic production of TNF has been implicated in a number of diseases including AIDS and cancer (Tracey and Cerami, Annu. Rev. Med., 1994, 45, 491-503). To date, two distinct TNF cell surface receptors, known as TNFR1 and TNFR2, have been described. Molecular analysis of TNFR1 and TNFR2 have shown that the two receptors share little homology in their intracellular domains and appear to activate distinct intracellular pathways (Tracey and Cerami, Annu. Rev. Med., 1994, 45, 491-503).
Recent studies with transgenic TNFR1 knockout mice have demonstrated that signaling through TNFR1 plays an important role in the clearing of low-level bacterial infection as well as TNF-induced septic shock following high-level bacterial infection (Lotz et al., J. Leukoc. Biol., 1996, 60, 1-7). These findings indicate that agents which can inhibit signaling through the TNFR1 receptor may serve as useful targets inhibitors of TNF induced toxicities such as septic shock.
Antisense oligonucleotide inhibition of TNFRl has proven to be a useful tool in understanding the role of TNFR1 stimulation in cytokine induction and cell proliferation. Ojwang et. al. have disclosed partial phosphorothioate antisense oligodeoxynucleotides containing C-5 propynyl or hexynyl derivatives of 2'-deoxyuridine which caused attenuation of TNFR1 mRNA and protein and inhibited TNF-alpha induced expression of IL-6 in MRC-5 cells (Ojwang et al., Biochemistry, 1997, 36, 6033-6045). These oligonucleotides were targeted to the poly(A) signal site of TNFR1 mRNA. A uniform phosphorothioate oligodeoxynucleotide targeted to the translation initiation codon of TNFR1 was found to have no effect.
There remains a long-felt need for improved compositions and methods for inhibiting TNFR1 gene expression.